This invention relates generally to apparatus for administering general anesthetics in the gaseous state and more particularly to an anesthesia rebreathing system, comprised of a permanent portion and a disposable portion:
The use of conventional general anesthesia administration apparatus inherently involves the danger of cross contamination between patients, sometimes with fatal results. Typically, such apparatus, for example an anesthesia circle, is comprised of one way valve controlled inspiratory and expiratory tubes communicating between an anesthesia machine providing fresh gases, and a patient. The inspiratory and expiratory tubes generally communicate with the patient's lungs via a tubular Y-piece and a mask or endotrachael tube. At the anesthesia machine end of the system, the expiratory tube normally communicates with the upper end of a canister of CO.sub.2 absorber material. The lower end of the canister is coupled to the machine end of the inspiratory tube and to a gas reservoir such as a breathing bag. The fresh gas input from the anesthesia machine is usually coupled to the inspiratory tube close to the breathing bag. On expiration, the patient's gas is channeled through the one way valve in the expiratory tube to the CO.sub.2 absorber material. On inspiration, the patient's gases are pulled through the inspiratory tube via the one way inspiratory valve, from the breathing bag and fresh gas supply. A pop-off valve is normally located proximate to the CO.sub.2 absorber canister for exhausting expired gas.
It will, of course, be readily appreciated that in the utilization of such anesthesia apparatus, various parts of the apparatus are exposed to gas expired by the patient, who, if infected, will transmit bacteria throughout these parts. It has been found that cultures taken from such patient exposed parts will grow bacteria after the apparatus has been subjected to such cleaning procedures as are considered practical for each particular part of the apparatus.
In recognition of the foregoing contamination problem, recent attempts have been made to sufficiently reduce the cost of anesthesia apparatus so that most of the patient exposed parts can be discarded after a single use. Generally, these attempts have merely involved fabricating conventional apparatus in an inexpensive manner so that disposal is economically feasible. Such attempts have not, however, been too successful because cost reduction has not been sufficiently significant and because such cost reduction has necessitated the introduction of performance compromises which have often adversely affected the reliability and ease of use of various parts, such as the pop-off valve.
Accordingly, one of the important objects of the present invention is to provide an anesthesia rebreathing system comprised of a disposable portion and a permanent portion configured so as to minimize the structural complexity and cost of the disposable portion, while assuring that the disposable portion includes all elements which are likely to contaminate gas inhaled by a patient.